Does the Blood Flow Up?

I can’t tell you how many times I have been asked that question when I present our aortic valve bypass concept to non-surgeons.

I no longer need to answer by referring the doubting Thomas’ only to the substantial body of clinical evidence published over the past 40 years demonstrating that apex to aorta valve bypass works just fine perfusing the coronaries, upper extremities, and the brain.  I can now  say – ask the Mayo Clinic.

Through collaboration with cardiac surgeons at the Mayo Clinic we recently completed a ten swine animal study – elegantly simple in design but technically challenging in implementation.  Using ultrasonic flow probes supplied by Medi-Stim, we measured blood flow simultaneously in eight arteries around the heart both before and after the graft was installed and with the native aortic valve completely occluded (simulating a worst case stenotic valve condition).  Flows were simultaneously measured in the:

  • LAD
  • Circumflex
  • RCA
  • Right Common Carotid Artery
  • Right Internal Mammary Artery
  • Ascending Aorta (above graft anastomosis)
  • Descending Aorta 9 below AVBG anastomosis
  • Pulmonary Artery

The bottom-line result:  none of the flows significantly changed after the native aortic valve was totally occluded except flow in the descending aorta above the graft anastomosis immediately reversed from downward to upward.   Also, a key finding was that there was no change in coronary flows.

Although surgeons know this procedure works, the effect on nearby and systemic circulation due to the altered outflow path has never been carefully measured.  Some researchers have performed theoretical flow calculations predicting acceptable retrograde flows to the coronaries and carotids, but to my knowledge no one until now had ever directly measured blood flow in all the major arteries surrounding the heart immediately pre and post graft implantation.

The study results were reported at the ISMICS annual conference in Washington on June 9.   Click to read the paper’s abstract.  Based on this work, lead investigator Dr. Nikolaos Tsirinkos-Karapanos was awarded the prestigious Robert Emery Young Investigator Award.

Congratulations to Dr.  Tsirinkos-Karapanos and the entire team at Mayo.  Through their scientific inquiry, a fundamental question about AVBG has been answered.  No doubt, the now widely accepted Coronary Artery Bypass Graft (CABG) procedure, having similar non-physiological flow, had to answer a similar question early in its path to broad clinical acceptance.

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